1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing bundles of semipermeable hollow fibers for a membrane device.
More particularly, the invention relates to manufacturing bundles of hollow fibers for constituting the membrane of exchanger type devices in which the membrane delimits two compartments through which fluids of different kinds are caused to flow in order to cause transfers to take place from one fluid to the other by diffusion and/or by convection. By way of example, mention may be made of hemodialyzers which are used to purify the blood of patients suffering from kidney failure.
2. Description of the Related Art
For any given kind of membrane, the efficiency of an exchanger is related mainly to the way in which the bundle of fibers is structured, with efficiency being maximal when the fluid flowing over the outsides of the fibers is constrained to flow uniformly between the fibers and is prevented from clearing itself preferential paths through the bundle.
European patent No. 0 093 677 describes a method of manufacturing bundles of hollow fibers enabling bundles to be obtained of a structure which is optimal with respect to exchanges between fluids in the devices in which they are installed. This method consists in forming a sheet of fibers on a drum of polygonal section by winding a fiber on the drum while causing it to move back and forth regularly from one end of the drum to the other. The tubular sheet obtained in this way is thus constituted by a plurality of layers of turns, with the turns in any layer being at a substantially constant angle relative to the turns of the adjacent layers. Once it has been made up, the sheet is secured to the drum along each of the edges of the drum and is then cut up along said edges into as many sheet portions as the polygonal section of the drum has sides. The sheet portions are then removed from the drum and are rolled up individually about an axis perpendicular to the lines of cut to form bundles of hollow fibers ready for installing in the housings of membrane devices.
Manufacturing bundles of hollow fibers from the sheet formed on the drum in accordance with that method requires quite a large number of manipulations and this is detrimental to industrial throughput and to uniformity of the manufactured bundles. In addition, that method requires as many different drums to be available as there are different lengths of bundle to be manufactured, or else it requires large quantities of fiber to be discarded when manufacturing smaller sized bundles.